While smoking rates have been declining within the U.S. general population for the past 4 decades, the Northern Plains tribes (which include the Oglala Sioux and other Lakota tribes) have experienced high rates of commercial tobacco use. The prevalence of smoking among these tribal groups is greater than 50% in many communities, roughly 2.5 times higher than the U.S. general population. Our primary study objective is to develop and test a culturally tailored educational intervention to encourage adoption of home smoking restrictions in Northern Plains' tribal households where children are present. We will conduct a randomized, controlled trial to test a novel biomarker feedback intervention. We will randomize 180 households to either receipt of educational materials only (control group), or receipt of educational materials plus information on urine toxin levels (e.g., cotinine and tobacco-specific nitrosamines) present in one child from the household (biomarker intervention). Cotinine is a well-recognized marker of exposure to tobacco smoke, and the intervention will provide feedback to smoking households about their children's actual exposure to environmental tobacco smoke. The primary outcome of this study will be the adoption of home smoking restrictions verified by a household air quality monitor. Our scientific aims are to: 1) Evaluate the impact of the child urinary toxin biomarker feedback intervention on the adoption of home smoking restrictions and on home air quality; 2) Determine the effect of the intervention on health-related quality of life 3 and 6 months after implementation of the educational and biomarker feedback intervention; Determine the effect of the intervention on adult smokers' cigarette use, including readiness to quit, quit attempts, and cessation; 4) Assess how the intervention changes cultural and social factors that relate to smoking behavior, such as traditional tobacco use and family support. We hypothesize that the intervention with child toxin biomarker feedback will increase the adoption of home smoking restrictions, beyond the effect of just receiving a brochure and education.